One of the most well-known semi-permanent fasteners is a hook-and-loop fastener having the brand name of Velcro. Hook-and-loop fasteners consist of two components: typically, two lineal fabric strips (or, alternatively, round dots or squares) which are attached (e.g., sewn, adhered, etc.) to the opposing surfaces to be fastened. The first component features tiny hooks; the second features even smaller and “hairier” loops. When the two faces are pressed together, the hooks catch in the loops and the two pieces fasten or bind temporarily. When separated, by pulling or peeling the two surfaces apart, the Velcro strips make a distinctive ripping sound. The first Velcro sample was made of cotton, which proved impractical and was replaced by Nylon and polyester. Velcro fasteners made of Teflon loops, polyester hooks, and glass backing are used in aerospace applications, e.g. on space shuttles.
Permanently locking fasteners are generally known and made of conventional metals, such as aluminum, brass, copper and steel, e.g., case hardened steel and stainless steel. These conventional metals and alloys deform via the formation of dislocations, i.e., plastic work. For these conventional metals, the fabrication processes can mostly be placed into two categories—forming and cutting. Forming processes are those in which the applied force causes the material to plastically deform, but not to fail. Such processes are able to bend or stretch the metal into a desired shape. Cutting processes are those in which the applied force causes the material to fail and separate, allowing the material to be cut or removed. While the currently available fasteners are effective, an ever continuing need exists for permanent or semi-permanent fasteners, particularly tamper-resistant fasteners for electronic devices.
Tampering involves the deliberate altering or breaking open a product, package, or system. Tamper-resistance is resistance to tampering by either the normal users of a product, package, or system or others with physical access to it. There are many reasons for employing tamper-resistance. Tamper-resistance ranges from simple features like screws with special heads, more complex devices that render themselves inoperable or encrypt all data transmissions between individual chips, or use of materials needing special tools and knowledge. Tamper-resistant devices or features are common on packages to deter package or product tampering. In some applications, devices are only tamper-evident rather than tamper-resistant.
It has been argued that it is very difficult to make simple fasteners, particularly for electronic devices, to secure against tampering, because numerous types of attacks are possible. Yet, there is a need for a simple, but effective, permanent or semi-permanent fastener that would at least obviate physical tampering or make the fastener, and possibly the device to which the fastener is attached, non-functional if the fastener has been tampered with.